A family of smad proteins that undergo PHOSPHORYLATION by CELL SURFACE RECEPTORS in response to TRANSFORMING GROWTH FACTOR BETA; ACTIVIN; or BONE MORPHOGENETIC PROTEIN signaling.

Synonyms: Smad Proteins, Receptor Regulated, 0, Receptor Regulated Smad Proteins, R-Smad Proteins, Smad Proteins, Receptor-Regulated, Receptor-Regulated Smad Proteins